import java.util.concurrent.ThreadPoolExecutor;

/**
 * @Author Weton Li
 * @Date 2021/3/22 22:49
 */
public class Day0322 {


    public static void main(String[] args) {
        int[] arr = {21,20,21,22,23,24};
        for (int i = 0; i < arr.length; i++) {
            for (int j = 0; j < i; j++) {
                if (arr[i] == arr[j]){
                    i--;
                    break;
                }
            }
        }
//        .-----


        
        for (int i = 0; i < arr.length; i++) {
            System.out.println(arr[i]);
        }
    }

}
